Numerous types of enclosures exist which are supplied continuously with a fluid, which, depending on the applications, may be a liquid, a gas or a liquefied gas, used alone or in a mixture. Generally, it is desirable to distribute the fluid within the enclosure in a homogeneous fashion, that is, in the same manner for any transversal cross-section of the enclosure.
It may be the case, for instance, of a chemical reactor, supplied with a charge to be processed, or a heat exchanger, supplied with a liquid or gaseous primary fluid, wherein are submerged pipes carrying a secondary fluid.
These enclosures are often spherically shaped and are generally supplied at their base or at their top through a conduit, which often exhibits an elbow, in the immediate vicinity of its connection to the enclosure. Yet, it is known that the presence of such an elbow causes variations in the flow speed of the fluid, thus significantly disturbing its distribution within the enclosure. Where this enclosure is, for instance, a chemical reactor comprising a fixed catalyst bed, these disturbances may cause physical distortions at the top of the catalyst bed in terms of the arrangement of catalyst pellets, create waves on the surface of the bed, or encourage movements of catalyst fines, all of which hamper the ideal operation of the reactor.
It is therefore advantageous and even essential to distribute the fluid in the most homogeneous fashion possible at the top of the enclosure, particularly of a reactor, in order to minimize operating incidents caused by upsetting the surface of the catalyst bed and, consequently, to increase the duration of the operating cycle.
In order to meet these requirements, various types of homogenization and distribution systems have been proposed to date.
Thus, it has been suggested that a pre-distributor be placed inside the supply conduit, downstream of the elbow which it may comprise, and upstream of the opening by which it discharges into the enclosure being supplied, and, preferably, a second distributor downstream of this opening.
It was thus proposed that, for single-phase flows, a simple plate, located transversally within the supply conduit and pierced with holes distributed in a substantially regular fashion across its entire surface, be used as the pre-distributor.
Such a perforated plate considerably improves the homogeneity of the distribution of a fluid, for instance, water vapor having a relatively high flow speed (in excess of 5 m/s). In addition, it significantly diminishes the effects caused by the presence of an elbow on the supply conduit, upstream of the plate. The use of such a plate, in the case of a single-phase flow, therefore appears highly advantageous; however, its use is limited to this type of application.
It was also proposed that a static mixer be used at the output of the supply opening within the enclosure. Such mixers are essentially provided for laminar flows, especially flows of mixtures of highly viscous fluids, or mixtures or dispersions of liquids with highly different viscosities, in order to significantly improve the homogeneity of multiphase mixtures and reduce gas-liquid discontinuity in particular.
These static mixers, nevertheless, have the inconvenience of occupying a considerable height within the enclosure, often at the expense of catalyst mass.
Among the distribution systems often used downstream of the pre-distributors mentioned above, the following will be mentioned, particularly for the distribution of gas phases:                distributors comprising an element shaped as a perforated spherical cap, the concave side of which faces the pre-distributor, and the surface of which comprises orifices of variable size, distributed in a rather uniform fashion;        distributors comprising an element generally shaped as a truncated cone, located downstream of the pre-distributor, the end with the smaller cross-section facing the pre-distributor;        diffusers comprising at least two coaxial pipes inserted into the supply conduit from the enclosure being supplied, these pipes being connected to flared, e.g., truncated cone-shaped, sections within this enclosure.        
All these distribution systems, as well as most of those available on the market, act on the stream of supply fluid by deflecting the direction of its flow and have considerable efficiency. They must, however, be adapted to each individual case, and their design depends—particularly and to a very large extent—on the flow rate of the fluid being distributed, which significantly increases their manufacturing cost.
Furthermore, all such assemblies consisting of a pre-distributor and distributor for the fluid cannot provide, at the same time:                a minimum speed of the fluid impacting the surface of the catalyst bed, on the order of, e.g., 1 m/s or below, when the flow rate of the charge varies from roughly one hundred tons per hour to several hundred tons per hour. Indeed, such low speeds minimize physical disturbances on the surface of the catalyst bed caused by the fluid impacting upon it more or less severely and also reduce the creation of catalyst fines caused by the charge recirculation phenomena in the space between the surface of the catalyst bed and the internal upper wall of the reactor;        a significant reduction in the residence time of the charge in the reactor minimizing the formation of gums on top of the catalyst bed. Indeed, it is known that the presence of such gums leads to charge losses within the reactor, which in turn reduces the unit's cycle time;        a significant increase in the flow rate of the charge without a degradation in the quality of its distribution within the reactor and particularly on any transversal surface thereof, more particularly, on the surface of the catalyst bed; and finally,        an increased volume of the catalyst bed obtained by reducing the bulk occupied by the pre-distributor and distributor assembly.        